1. Field of the Invention
The present invention relates to an electrodeposition display device which performs display with the electrodeposition method, and more particularly, to an electrodeposition display device with high memory capabilities and which can be driven with lower electrical power consumption.
2. Description of the Related Art
In recent years, advances in information display devices has led to the need to display devices which are thin and consume little electric power. At the center of interest is the liquid crystal display device, which is used in laptop computers and navigation systems, for examples, as a display device instead of conventional CRT displays. However, problems such as flickering and cross-talk and so forth have not yet been sufficiently solved with such liquid crystal display devices. Widespread development of new display devices is continuing to solve these problems.
An example of a device regarding which hopes are high to solve the problems of conventional liquid crystal display devices is the reflective display device. Reflective liquid crystal display devices have also been developed, but the electrophoresis display device, which is a new structure, is developing as a display device to replace liquid crystal display devices. The electrophoresis display device was invented by Harold D. Less et al. Japanese Patent Publication No. 6-52358 discloses an electrophoresis display device.
On the other hand, plating technology has been long known as an easy coating method, and plating techniques using various types of materials have been reported so far. One example is an electrodeposition technique called through-hole plating, which is often used for manufacturing printed wiring boards. Rapid advance of semiconductor integrated circuits has lead to increased density and layers in printed wiring boards. The width and intervals between the patterns have become narrow and small, the diameter of through-holes and lands reduced in size, and further increased layers is increasing the aspect ratio.
Through-hole plating is often carried out by the subtractive method. The steps are as follows: preparing a copper-clad laminate, opening holes, electroless copper plating, panel copper plating (primary electrolytic copper), photo-resist processing, pattern copper plating (secondary electrolytic copper), surface plating, etching, terminal plating, and finishing. Also, various methods for plating the through-hole parts have also been reported, one of which is Japanese Patent Laid-Open No. 10-56261.
Other methods for electrodeposition of metal within a pre-fabricated cell have also been reported. An example is given in J. Electrochem. Soc. Vol. 144 No. 6, P1923, Jun. 1997. A great many examples of applications using such electrodeposition are given, such as minute array electrodes, printed boards, GMRs, electron sources, various types of masks, and so forth. Application to even more fields is expected by further improvement in capabilities.
However, conventional display devices have had the following points demanding improvement. That is to say, there have been problems of poor memory capability at times, with a phenomena occurring wherein display completely disappears or contrast gradually becomes weaker upon stopping application of potential. In other words, there has been the need to continuously apply potential in order to maintain the displayed state, necessitating improvement from the perspective of cost. Also, demanding high-responsivity at high contrast has required voltage of several dozen volts or higher, meaning that the electric consumption is great.
The present invention has been made in light of the above-described problems, and accordingly, it is an object thereof to provide an electrodeposition display device with high memory capabilities which can be driven with lower electrical power consumption, and further be capable of readily replacing display color for each cell, by using the electrodeposition method.
To achieve the above objects, the electrodeposition display device according to the present invention comprises: a first substrate; a second substrate facing the first substrate; walls for sealing off the substrates; plating liquid sealed in between the substrates so as to form a cell; a first electrode disposed on at least a part of the first substrate; and a second electrode disposed within the cell; wherein display is performed by applying signals corresponding to image information to the first electrode and the second electrode, so as to change the state thereof to a state wherein electrodeposition of metal has occurred on at least part of the first electrode, and a state wherein at least a part of metal on the first electrode has become disassociated.
The second electrode is preferably on at least the second substrate, the walls, or the first substrate. A plurality of the second electrodes may exist within the sealed cell.
The current density for the electrodeposition is preferably within the range of 1 to 100 mA/cm2, and the metal is preferably nickel, copper, or cobalt.
The walls are preferably formed of anodic porous alumina, and the first substrate may be the front side or rear side of the device.
Also, with an arrangement wherein a plurality of the first electrodes and a plurality of the second electrodes are arrayed in matrix form, with cells disposed at the intersections between the first electrodes and the second electrodes, the device preferably further comprises: first driving means for applying scan signals or data signals to the first electrodes; and second driving means for applying data signals or scan signals to the second electrode.
Thus, a display device with high memory capabilities which can be driven with lower electrical power consumption can be realized. Also, the display color for each cell can be easily replaced, facilitating color display, and color display is particularly easy in the event of using anodic porous alumina.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.